1. Field of the Invention
The invention relates to a particulate matter control system and its failure determination method.
2. Description, of Related Art
There is known a technique in which a discharge electrode is provided in an exhaust pipe of an internal combustion engine and corona discharge is generated from the discharge electrode to electrically charge particulate matter (hereinafter, also referred to as PM) to thereby aggregate PM (for example, see Japanese Patent Application Publication No. 2006-194116 (JP 2006-194116 A)). By aggregating PM in this way, the particle number of PM may be reduced. In addition, the particle diameter of PM increases, so PM may be easily trapped by a filter provided on a downstream side.
Incidentally, because of a failure or degradation of the particulate matter control system, it may be difficult to aggregate PM. For example, even when a detected applied voltage and a detected current are normal, there is a case where PM cannot be caused to aggregate.